The invention is based on an apparatus for avoiding locking of the wheels of a vehicle equipped with a brake system.
An apparatus of this kind has already been proposed (German Patent Application P 39 04 132.8), a corresponding patent application has been filed in the United States on Dec. 1, 1989, Ser. No. 444,246, in which the valve assembly between the master brake cylinder and the pump comprises a 2/2-way valve and a bypass valve. This bypass valve, embodied as a check valve, is open only from the master brake cylinder to the pump or to the wheel brakes. If the 2/2-way valve is reversed in its switch position by the pressure in the master brake cylinder in a braking event, then in the anti-skid mode of the known apparatus, pressure pulsations originating from the pressure reduction in the wheel brake, which are annoyingly perceptible at the brake pedal, are largely diminished by the throttling action of the 2/2-way valve. However, when pressure fluid flows back out of the master brake cylinder for the pressure buildup in the wheel brake, the throttling 2/2-way valve is bypassed via the bypass valve, which leads to perceptible, undesirable pulsations at the brake pedal.